Liquid crystal devices for practical use include TN (twisted nematic) or STN (super-twisted nematic) mode displays using nematic liquid crystals. Those utilizing ferroelectric liquid crystals have also been proposed.
The conventional devices require a polarizer and are therefore limited in brightness of the display.
It is known that use of a polymer film having dispersed therein microencapsulated liquid crystals makes it possible to produce large-sized and still inexpensive and high-contrast liquid crystal devices requiring neither a polarizer nor an alignment layer. Encapsulating materials proposed to date include gelatin, gum arabic, polyvinyl alcohol, etc. as disclosed in JP-W-58-501631 (the term "JP-W" as used herein means an "unexamined published international patent application") and U.S. Pat. No. 4,435,047. Such polymer-liquid crystal dispersed systems also include a dispersion of liquid crystals in an epoxy resin matrix (JP-W-61-502128), a film in which phase separation between liquid crystals and a polymer is fixed on exposure to light (JP-A-61-305528; the term "JP-A" as used herein means an "unexamined published Japanese patent application"), a dispersion of liquid crystals in a special ultraviolet-curing polymer (JP-A-62-2231), and a process for filming a mixture of polyester, liquid crystals, and a solvent (JP-A-63-144321).
However, the liquid crystal devices obtained by the techniques disclosed in JP-W-58-501631, JP-W-61-502128, and JP-A-61-2231 need a high driving voltage of at least 25 V and, in most cases, from 50 to 200 V for obtaining sufficient transparency. Further, the contrast ratio achieved with the liquid crystal devices disclosed in JP-A-61-305528 and JP-A-162615 is 10 at the highest and, in most cases, 8 or less, which is below the level required for practical use.
In order to satisfy the above-described characteristics of liquid crystal devices which are important for practical use, i.e., low power driving properties, high contrast, and multiplex driving properties, JP-A-1-198725 discloses a liquid crystal device having such a structure that a liquid crystal material forms a continuous phase in which a polymer forms a three-dimensional network.
The disadvantage of the above-mentioned light scattering type liquid crystal devices, when used as a display panel, is that the background black or any other color is not cut off even with no voltage applied and is slightly visible through opaqueness because of utilization of light scattering. This has made display of direct view type difficult, and particularly made full color display impossible.